In these days, an organic luminescence material has been developed. The organic luminescence material has characteristics of emitting a light when a forward current is applied to two electrodes interposing the organic luminescence therebetween.
The organic luminescence material can emit a light having a red wavelength, a light having a green wavelength and a light having a blue wavelength according to the characteristics thereof.
Recently, an organic EL device has been developed by using the characteristics of the organic luminescence material. The organic EL device is lighter in weight and smaller in size than that of an LCD (Liquid Crystal Display) device.
In order to display an image in a full-color in the organic EL display device, the organic EL requires an anode electrode, a cathode electrode and an organic luminescence layer having the organic luminescence material interposed between the anode and the cathode electrodes.
The anode electrode is disposed on a transparent substrate in a matrix configuration. The number of the anode electrode is three times as many as a resolution of the organic EL device. The anode electrode is connected with a thin film transistor disposed in the matrix configuration. The anode electrode is made of a transparent conductive material such as an ITO (Indium Tin Oxide) or an IZO (Indium Zinc Oxide).
The thin film transistor includes a gate electrode, a source electrode, a drain electrode and a channel layer. The gate electrode of the thin film transistor is connected with a gate line, and the source electrode of the thin film transistor is connected with a data line.
FIG. 1 is a cross-sectional view showing a conventional organic EL device.
Referring to FIG. 1, an anode electrode 1 is connected with the drain electrode of the thin film transistor. The anode electrode 1 supplies holes to the organic EL material.
The organic EL material includes a red organic EL material 4 for emitting a light having a red wavelength, a green organic EL material 6 for emitting a light having a green wavelength and a blue organic EL material 8 for emitting a light having a blue wavelength. The red, green and blue EL materials 4, 6 and 8 are disposed on the anode electrode 1.
The cathode electrode 10 is disposed on the red, green and blue organic EL materials 4, 6 and 8 so as to supply electrons coupled to the holes provided from the anode electrode 1. The cathode electrode 10 is comprised of a pure aluminum or an aluminum alloy, and is disposed with a uniform thickness on a substrate to cover the anode electrode 1.
However, the organic EL materials 4, 6 and 8 are weak to oxygen and moisture in an atmosphere. When the organic EL materials 4, 6 and 8 are exposed to the oxygen and the moisture, a macromolecule chain of the organic EL materials 4, 6 and 8 is disconnected, or the organic EL materials 4, 6 and 8 are deteriorated because the organic EL materials 4, 6 and 8 react chemically with the oxygen and the moisture.
As a result, the organic EL materials 4, 6 and 8 cannot emit a light of required wavelength, or a life of the organic EL materials 4, 6 and 8 are rapidly reduced.
Accordingly, the organic EL materials 4, 6 and 8 should not be exposed to the oxygen and the moisture in the atmosphere when the anode electrode, cathode electrode and the organic EL materials 4, 6 and 8 are formed.
For this purpose, the organic EL materials 4, 6 and 8 are isolated from the oxygen and the moisture in the atmosphere by means of a metal can 12 and a sealant 12a. As shown in FIG. 1, a terminal part 14 of the cathode electrode 10 is not sealed by means of the metal can 12 and is exposed to the oxygen and the moisture in the atmosphere.
When the terminal part 14 of the cathode electrode 10 is exposed to the oxygen and the moisture in the atmosphere, an exposed portion of the terminal part 14 is oxidized, so that electrical characteristics of the cathode electrode 10 and display characteristics of the organic EL device are deteriorated.